Method for making a vehicle window panel using a melt-processible gasket material

ABSTRACT

A vehicle window panel assembly and a manufacturing method for such assemblies having a gasket made from a melt-processible material and providing a long-term, failure-resistant bond between the gasket and window panel for retaining the window panel assembly in the vehicle. The gasket material provides a bond which resists both short- and long-term dynamic and static loads exerted on attachment members embedded in the gasket to prevent failure or separation between the gasket member and the window panel assembly for prolonged assembly life and substantial saving to vehicle manufacturers and owners. A method for identifying and selecting the melt-processible material for forming the gasket member is also disclosed.

CROSS REFERENCE TO RELATED APPLICATION

This is a division of U.S. patent application Ser. No. 08/289,378, filedAug. 12, 1994, now U.S. Pat. No. 5,635,281.

FIELD OF THE INVENTION

The present invention relates to vehicular window panels, andparticularly to a single- or two-sided gasketed window assembly andmethod of selecting melt-processible materials for such assemblies, aswell as a method for selecting materials enabling secure, long-termattachment of the window panel to the vehicle under short- and long-termstatic and dynamic loads.

BACKGROUND OF THE INVENTION

Conventional modular vehicle window panels consist of at least one panelof glass shaped to generally fit in an opening defined by the sheetmetal of the vehicle and sealed therein by a gasket attached to theperipheral edge of the glass panel. Traditionally, the gasket was formedsuch that the gasket completely enclosed the peripheral edge of thepanel and included flanges which extended inwardly on opposing surfacesof the panel. This "three-sided encapsulation" provided mechanicalanchoring of the gasket to the panel.

Contemporary modular vehicle window panels may have a gasket formed onat least one surface of the panel along the peripheral edge of the panelbut do not have gasket material extending onto the exterior surface.Such gaskets are formed along the inner surface of the panel proximatethe peripheral edge and are known in the art as single-sidedencapsulation. Other shapes or forms of gaskets include a portion whichwraps partially around and onto the peripheral edge but does not extendonto the exterior surface and are known in the art as two-sidedencapsulation. The two-sided encapsulant gasket along the peripheraledge can be flush with the exterior surface of the panel. Single-sidedor two-sided gasketed panels have been sometimes designated "flushglazings or panels" because of the absence of gasketing materialextending onto the exterior surface of the panel and because of theirability to facilitate mounting of window glazings generally flush withthe exterior of the sheet metal body of the vehicle.

A problem with single- or two-sided encapsulant glazings or panels isthat they do not offer the mechanical retention of the window offered by"three-sided encapsulant" modular windows. In the case of single- ortwo-sided gasketed panels, the gasket may be bonded to the sheet metalor the glass panel may be bonded to the sheet metal to retain the glassin the window opening such as by use of an adhesive. Mechanicalfasteners have also been used to retain the modular panel in the windowopening. An example of one specific mechanical fastener includes a studpartially encapsulated by the gasket material located about or near theperipheral edge of the panel. The stud may have a head spaced from thepanel and encapsulated in the gasket material such that the stud floatswith respect to the panel. The stud also includes a shaft which extendsthrough the sheet metal of the window opening and is secured such as bya nut to retain the panel in the vehicle. Although a stud is one type offastener used, others may also be used including clips and ratchetedstuds or trees.

In terms of selection of gasketing material, prior artisans have used avariety of melt-processible materials for window encapsulation, withinjection molding of plasticized polyvinylchloride (PVC) resin enjoyingcommercial success, particularly for three-sided encapsulation, and haveused materials, principally thermosetting urethanes, that are not meltprocessible, but are rather formed by liquid injection molding such asin reaction injection molding (RIM) of polyurethane. Melt processing isa desirable technique for fabrication of the gaskets of this inventionfor a variety of reasons. For example, melt processing involvesprocessing at elevated temperature, such as in excess of 100° C., and isamenable to formation of gaskets onto substrates that are themselvesheated. Such elevated temperature is useful for enhancing adhesionbetween the gasket and the window panel. Also, unlike RIM ofthermosetting urethane, melt processing allows potential use of a widevariety of materials, both thermoplastic and thermosetting, with theadded advantage of allowing formation using melt processing ofrecyclable gaskets that are desired to assist preservation of theenvironment.

However, although in the past a wide variety of melt-processiblematerials, such as PVC, have been suggested for forming gaskets such assingle- or two-sided gaskets, particular attention has not been paid tothe long-term bonding characteristic of the gasket to the glass when theassembly is attached to the vehicle by mechanical fasteners floating inthe gasket material. Loads imposed on the fasteners embedded in thegasket are transferred to the bond line between the panel and thegasket. The types of loads include tensional-loads or off-form loadscaused by differences or variations in the shape of the window panel andthe sheet metal opening; static loads on the panel assembly itselfcaused by the weight of the glazing on the fasteners; and dynamic loadsimposed on the studs through normal use, including vibration of thevehicle, acceleration/deceleration of the vehicle, wind and air pressureon the interior and exterior of the vehicle, and other activities suchas the opening and closing of the vehicle doors.

In single- and two-sided encapsulations such as those described above,it has been found that over time, the bond between the panel and thegasket may fail in adhesion in an area localized about the fastener.Such failure can result in water leaks, wind noise, and rattling of thewindow panel in the vehicle opening. Previous solutions to theseproblems include directly attaching the fastener to the glass panel sothat the loads are transferred directly to the window panel instead ofto the gasket, or even dispensing with fasteners and utilizing directgasket-to-vehicle adhesion using an adhesive applied substantiallybetween the gasket and vehicle opening. Such attachment methods resultin extra processing and may be time-consuming resulting in additionalcosts in the panel. Other solutions include closer stamping tolerancesand fabrication of the welding of the window opening, which also mayresult in increased time and labor expenditures resulting in a moreexpensive product. Additional solutions include use ofnon-melt-processible gasketing material such as RIM or thermosettingurethane with the consequent loss of the benefit associated with meltprocessing described above.

SUMMARY OF THE INVENTION

The instant invention is directed to a vehicle window assembly and amethod incorporating the selection of materials for single- or two-sidedvehicle panel gaskets or grommets and which comprise at least onemechanical fastener partially encapsulated by the gasket material aboutor near the peripheral edge of the panel. The fastener often includes ananchor or head spaced from the panel and encapsulated in the gasketmaterial such that the fastener floats with respect to the panel. Theinvention provides long-term bonding of the gasket with the glazingunder dynamic and long-term static loads. Such long-term bonding isachieved using a method for selecting a melt-processible material forforming single- or two-sided encapsulations having a multi-phasemorphology and which are resistant to tensile creep. The multi-phasemorphology of the material is indicated by the variation of the elasticstorage modulus as a function of temperature, wherein the materialexhibits a rubbery plateau disposed between a lower transition point anda higher transition point and with the onset of the rubbery plateaucommencing at a temperature below about 50° C. (preferably, below about30° C.). The lower transition point marks the transition temperaturewhere the character of the material changes from a state exhibitingsignificant rigidity to a state exhibiting significant flexibility,while the higher transition point marks the transition temperature wherethe character of the material changes from a state exhibitingsignificant flexibility to a state exhibiting significant viscous flow.It is preferred that the lower transition point be less than 24° C.,preferably less than 0° C., and most preferably less than -20° C., whilethe higher transition point be greater than 60° C., preferably greaterthan 80° C., and most preferably greater than 100° C. The lowertransition point and the higher transition point both occur attemperatures within the range of automotive interest, which is betweenabout -50° C. to about +150° C.

Another form of the invention is directed to a method for manufacturinga vehicle window panel including providing a window panel having aperipheral edge and forming a gasket on the window panel from amelt-processible material having a multi-phase morphology. It ispreferred that the multi-phase morphology exhibit a rubbery plateaudisposed between a lower transition point having a temperature less than24° C., preferably less than 0° C., and most preferably less than -20°C., and a higher transition point having a temperature greater than 60°C., preferably greater than 80° C., and most preferably greater than100° C.

Another form of the invention includes a vehicle window panel includinga gasket attached to at least one side of the panel where the gasket ismade from a melt-processible material exhibiting a multi-phasemorphology. The multi-phase morphology exhibits a rubbery plateaudisposed between the transition points as defined above.

Yet another form of the invention relates to the economical use ofmelt-processible gasketing materials that are cross-linkable to providelong-term bonding of the gasket under dynamic and long-term staticloads.

And, yet another form of the invention relates to novel mold designsparticularly well adapted for economical molding of large areaautomotive modular windows such as the single- and two-sidedencapsulated windows of this invention.

The advantages provided by this invention include providing a windowpanel gasketing material which can be formed by melt processing such asby injection molding, compression molding, extrusion, and their like,and attached to the vehicle window panel in a variety of forms.Moreover, studs or other attachment members can be partiallyencapsulated by the gasket material and used for attaching the windowpanel to the vehicle without localized failure in the gasket-to-windowpanel joint caused by short- or long-term static and dynamic loads. Theintegrity of the seal between the vehicle window panel and the vehicleitself is sustained without the additional costs resulting from aseparate bonding of the stud directly to the window panel, orsubstantially reducing the tolerances between the shape of the vehiclepanel opening and the window panel itself. A window panel of improvedperformance is produced at a lower cost.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

A better understanding of the invention and the advantages providedthereby may be obtained by reference to the specification and theattached drawing figures, wherein:

FIG. 1 is a perspective view of a window panel in a vehicle;

FIG. 2 is a section view through the peripheral edge of the window panelshowing an attachment member in the window panel gasket and passingthrough a flange forming the window opening;

FIGS. 3-6 illustrate alternative profiles of various single-sided andtwo-sided encapsulant gaskets in accordance with this invention;

FIG. 7 is a graph illustrating the elastic storage modulus versustemperature curve for a model material having a multi-phase morphology;

FIG. 8 is a graph illustrating the elastic storage modulus versustemperature for conventional PVC (single-phase) gasket material;

FIGS. 9-12 illustrate multi-phase morphologies of several materials;

FIGS. 13-16 are graphs illustrating creep strain as a function oftemperature for various materials at various temperatures;

FIG. 17 is an elevational section view through one embodiment of aninjection mold apparatus suitable to insert mold a static spacer,gasket, or grommet on a single surface of a window panel;

FIG. 18 is an elevational section view of another embodiment of aninjection mold apparatus suitable to insert mold a static spacer,gasket, or grommet simultaneously on two glass panels;

FIG. 19 is an elevational section view of yet another embodiment of aninjection mold apparatus suitable to insert mold a static spacer, orgasket simultaneously on two glass panels, and illustrating attachmentmembers suspended in the mold cavity;

FIG. 20 is an elevational section view of yet another embodiment of aninjection mold apparatus suitable to insert mold three-sidedencapsulations simultaneously about at least two glass panels;

FIG. 21 is an elevational section view illustrating one embodiment of astacked-cavity injection mold apparatus used to simultaneously form thestatic spacer or gasket on at least two vehicle window panel assembliesand how each window panel is located within the mold;

FIGS. 22A, 22B, 22C, and 22D illustrate operation of the stacked-cavityinjection mold apparatus and the molding process for simultaneouslyforming the gaskets on the window panels;

FIG. 23 graphically illustrates the adhesion characteristics of severaladhesive primers used in the invention; and

FIG. 24 illustrates a plot of elastic storage modulus versus temperaturefor various materials.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of the following description, the terms "upper,""lower," "right," "left," "front," "rear," "vertical," "horizontal," andderivatives or equivalents thereof shall relate to the invention asoriented in FIGS. 2 to 24. It is understood that the invention mayassume various alternative orientations, except where expresslyspecified to the contrary. It is also understood that the specificdevices and processes illustrated in the attached drawings, anddescribed in the following specification, are simply exemplaryembodiments of the inventive concepts defined in the appended claims.Hence, specific dimensions and other physical characteristics relatingto the embodiments disclosed herein are not to be considered limitingunless the claims expressly state otherwise.

Referring to FIG. 1, a vehicle 10 contains at least one fixed windowpanel assembly 14 mounted in a window opening 12 formed by the sheetmetal exterior of the vehicle body. Traditionally, the vehicle windowassembly 14 includes one or more sheets of transparent glass generallyshaped to fit in the window opening. Recently, the trend has been toproduce vehicle window panels where the gasket is attached to at leastthe interior surface of the panel to produce a flush glazing, such thatthe exterior surface of the panel is generally flush with the exteriorof the sheet metal body. Such flush glazings are retained in the windowopening using various techniques including adhesives and/or mechanicalattachments.

A preferred embodiment of the window panel assembly 14 (FIG. 2) includesa panel or sheet 16, preferably of transparent, tempered, laminated, orotherwise strengthened glass formed using conventional techniques andprinciples, with two substantially parallel sides, surfaces, or faces18, 20, which terminate at a peripheral edge 22. Although transparentglass is preferred, other sheet-like panel materials may be used such asopaque or coated glass, transparent-coated or opaque plastic materials,or multi-composite laminates such as transparent glass and plastic.Optionally, and preferably, deposited and bonded to the surface 18 ofpanel 16 is an opaque blackout layer such as a black frit layer, andmost preferably a ceramic frit layer or coating 24 covering andconcealing a region from peripheral edge 22 inward. Alternately, fritlayer 24 may cover all or substantially all of surface 18. Usually,however, frit layer 24 conceals a peripheral area of surface 18 nearedge 22, such as two or so inches in from edge 22.

Fixed to ceramic frit layer 24, and extending along and around at leasta portion of sheet 16 and spaced in from peripheral edge 22, is apolymeric form or bead, preferably flexible and resilient, which definesa static spacer, gasket, or grommet 26 (hereinafter referred to as"gasket") intended to engage pinch weld flange 12' of the window openingwhen installed. In the present invention, it is preferred that polymericgasket 26 be formed from a melt-processible material described ingreater detail below.

In one embodiment (FIG. 2), gasket 26 includes a body 28 of generallytrapezoidal cross-section having a first surface 30 in intimate contactwith, and bonded to, ceramic frit layer 24. An opposite surface 32includes a generally rectangular channel 34 which may extend along theentire length of spacer or gasket 26. Gasket 26 forms a spacer seal tobody 28. Channel 34, in turn, defines first and second flanges 36, 38,respectively, which run adjacent channel 34. Although it is preferredthat spacer seal gasket 26 have a width less than or equal to about 1.00inch (preferably less than about 0.75 inch, and more preferably, lessthan about 0.5 inch) and a thickness less than or equal to 1.0 inch, thethickness and width of gasket body 28 and flanges 36, 38 may varydepending upon the application of window panel assembly 14.

Disposed in gasket 26 is an attachment member 40 to position, guide, andfix panel assembly 14 within window opening 12. Attachment member 40includes a locating and/or mounting stud having a shaft portion 42terminating at one end in a circular or rectangular head portion 44.Head portion 44 and a portion of shaft 42 are encapsulated so as tofloat within gasket 26 such that the remaining portion of the shaftextends out from gasket 26 in a direction away from panel 16. It ispreferred that shaft 42 extend from surface 32 in a directionsubstantially perpendicular to panel 16. Head portion 44 and/or shaft 42may be fabricated of metal, plastic, composite, or their combination. Ifdesired, a nut or similar securing member 45 may be attached to theshaft on the opposite side of pinch flange 12', to pull gasket 26tightly against pinch flange 12' and retain panel assembly 14 in place.A bead of adhesive (not shown) may be located either on the panel 16 oron gasket 26 to further help retain and seal the panel assembly withinwindow opening 12. Alternatively, a butyl tape may be deposited inchannel 34 either adjacent or around stud shaft 42 to form awater-resistant seal with pinch flange 12'.

Alternate embodiments of the gasket which may be used in associationwith the window panel are endless and depend solely on the manufacturingtechnique. Such accepted melt-processing techniques in the industryinclude injection molding, compression molding, extrusion, blow molding,as well as others. Examples of different embodiments include a body 46(FIG. 3) of generally trapezoidal cross-section having a surface 48 incontact with frit layer 24. An opposite surface 50 includes a channel 52extending along the length of the gasket defined by flanges 54, 56.Extending from channel 52 is attachment member 40a, such as describedearlier, with a head 44a and portion of the shaft 42a partiallyencapsulated by the gasket material and spaced from the inner surface18a so as to float in the gasket body 46a. Extending from body 46a andouter flange 56, arcuately away from inner surface 18a around peripheraledge 22a, is a flange 58 intended to occupy and close the gap betweenthe vehicle sheet metal and the window panel so as to form a lip seal.In this embodiment, peripheral edge 22a of glass panel 16a is exposed.

Another form of the gasket 60 (FIG. 4), in the form of a two-sidedencapsulant, includes a body encapsulating an attachment member asdescribed earlier, but varies in that an arcuate flange 62 extends frombody 46b and conceals or covers the peripheral edge 22b of panel 16b toencapsulate a portion of surface 18b and peripheral edge 22b. Arcuateflange 62 again occupies and closes the space between the edge of thevehicle window opening and the window panel and acts to channel debrisaway from the window opening. This configuration can be reversed ingasket 60' (FIG. 5) so that the flange 64 has the concave portion 66oriented toward the vehicle interior while the convex portion 68occupies and closes the space between the vehicle and peripheral edge22c. The exterior of convex portion 68 provides a flush transitionbetween the vehicle sheet metal exterior and surface 20c of panel 16c.

Yet another embodiment of a gasket 69 (FIG. 6) includes a bulb seal 70extending from body 46d and outer flange 54d to occupy the gap betweenthe edge of the vehicle window opening and the window panel.

Each of the embodiments are shown as examples and are not intended to beexhaustive or otherwise limit the scope of the invention. Each may beformed from a variety of melt-processing techniques including thepreferred techniques of injection molding, compression molding, blowmolding, or extrusion from a melt-processible material having thecharacteristics described below. Furthermore, the gasketed assemblies ofthis invention may be made by forming the gasket using a melt-processingtechnique (such as by injection molding) along with any accompanyingattachment member, in a mold separate from the window glass panel,thereafter locating the panel on the formed gasket and forcing thegasket against the panel to promote gasket-to-panel adhesion, such as isdescribed in commonly assigned U.S. Pat. No. 5,443,673, the disclosureof which is incorporated herein by reference.

In one or more of the embodiments described above, it is contemplatedand preferred that prior to placing or forming the gasket on the windowpanel, the surface of the panel and/or gasket receives a primer oradhesion-promoting compound 25 (FIG. 2). Such primers oradhesion-promoting compounds improve adhesion of the gasket to thewindow panel. Typically, such primers or compounds 25 are applied tosurface 18 (FIG. 2) or to surface frit layer 24 thereon prior toreceiving gasket 26. One example of such a compound has an acrylic baseincluding an epoxy component, and may further include anadhesion-promoting agent such as a silane coupling agent, a titaniumcoupling agent, and a zirconium coupling agent. Such primers will beidentified below in greater detail.

Gaskets 26, 46, 60, 60', and 69, contemplated to be used in accordancewith this invention, are made from a melt-processible material whichrequires the application of heat to mobilize or melt the material. Heatis required to process the melt-processible material under conventionalmolding techniques such as injection molding, extrusion, blow molding,compression molding, and similar techniques.

In one embodiment of the method, a panel is provided with or without afrit layer applied to surface 18. The surface of the panel to receivethe gasket is preferably cleaned by wiping with a suitable solvent, suchas isopropyl alcohol, which removes oils or other dirt and debris. Thealcohol mobilizes any contaminants and evaporates in a short period oftime leaving substantially no residue to interfere or degrade theprocess. Following cleaning of the panel, and after sufficient time haslapsed to evaporate any remaining solvent, a primer adhesive is appliedto that portion or greater which will receive a molded gasket. Withrespect to the embodiments having a gasket such as shown in FIG. 2, itis preferred that application of the primer adhesive be constrained to alinear path on the frit layer proximate the peripheral edge of the glassand have a primer coating thickness within the range of about 0.01 and5.0 mils, preferably within the range of about 0.1 to 1.0 mils.

In one embodiment, the primer adhesive is applied by a sprayer, wiper,roller, extruder, or other technique to the preferred thickness. Sinceit is anticipated that use of this invention will typically involveproduction of a large number of panels, an automated applicationtechnique is preferred. One automated process is by a robotic applicatorwhich extrudes a precise coat of the primer adhesive to a definedportion of the panel. To accurately reproduce the robotic application ofthe primer adhesive, conventional robotic devices and accuratepositioning of the panel in reference to the robotic applicator areused.

Subsequent to the application of the primer adhesive, it is preferredthat the primer adhesive be heated to a temperature greater than 250°F., and most preferably to a temperature between 250° F. and 350° F.,usually 325° F., such as described in commonly assigned U.S. Pat. No.5,544,458, the disclosure of which is incorporated herein by reference.By heating to about 325° F., sufficient heat is retained in the panel,primer, and the frit layer so that the temperature will be above 250° F.after transfer of the panel from the heat source to a mold assembly andduring the molding process. It has been found that by heating the paneland adhesive primer to a temperature greater than 225° F. andmaintaining that temperature up through the time the gasket is formed onthe panel, an exceptionally strong bond and water resistant barrier isformed between the panel and the gasket. The minimum temperature for aprimer adhesive at which such a bond occurs is known as the "primertransition temperature." The primer transition temperature may also bedefined as that temperature for a given primer where the adhesivequality significantly changes.

                  TABLE I                                                         ______________________________________                                        Manufacturer                                                                              City, State                                                                             Designation                                             ______________________________________                                        B. F. Goodrich                                                                            Akron, OH A-1100-B plus A-1167-B at                                                     20:1 ratio                                              Donnelly Corp.                                                                            Holland, MI                                                                             A-57 (includes silane coupling                                                agent)                                                  B. F. Goodrich                                                                            Akron, OH EXP-541 plus EXP-535 at                                                       20:1 ratio                                              Donnelly Corp.                                                                            Holland, MI                                                                             A-47 (includes silane coupling                                                agent)                                                  ______________________________________                                    

Adhesive primers such as identified above in Table I, exhibit asignificant improvement in adhesion after being heated to a temperaturegreater than its transition temperature (usually at least 200° F.). andreceiving the molded gasket after heated to that temperature. For theprimers identified in Table I, the primer transition temperature isgenerally above 200° F. A better understanding of the improved adhesivecharacteristic and primer transition temperature definition may beobtained by referring to the graph shown in FIG. 23.

FIG. 23 graphically represents the results of experiments using theprimers in Table I in bonding a gasket to a single surface of a glasspanel such as 16 having a frit layer 24 thereon. The abscissa or X-axisis a plot of the temperature to which panel 16 and each primer 25 washeated to prior to the time the gasket was molded thereon. The ordinateor Y-axis of the graph is the number of hours the gasket survived shearand peel tests after soaking in water having a temperature of 80° C.Points were plotted when the cohesive character of the gasket failed,but not if the bond between the panel and the gasket failed. Cohesivefailure occurred when 80 percent or more of the gasket was retained onthe panel when subjected to both shear and 90° peel tests. Presently,the most stringent standard known to be followed by automobilemanufacturers is 100 hours. That is, the bond between a gasket and panelshould survive a minimum of 100 hours in the 80° C. water soak, and,preferably, at least 200 hours 80° C. water soak.

To provide consistent results, shear tests were conducted on gasketsbonded to a glass plaque, each gasket having a length of approximately1.0 inch, 0.75 inch wide, and 0.50 inch thick. The shear tests wereconducted transversely to the long axis of the gasket at a rate of 25millimeters per minute. Peel tests were conducted on gaskets 0.75 inchwide, 0.50 inch thick, and of a length sufficient to pull one end 180°back along the gasket at a rate of 25 millimeters per minute.

As seen in the graph, substantially every adhesive primer has animproved adhesive quality at a temperature above 200° F. with theexception of conventional primers that are water-based urethanes (curveE). For the adhesive primer designated A-1100 (curve B), a noticeableincrease in the slope of the curve occurs around 250° F., and the slopeshows another significant change around 290° F. The adhesive primerdesignated A-47 (curve D) follows a similar curve as does the preferredadhesive primer A-57 (curve C). Adhesive primer 541 (curve A) obtainsits maximum adhesion when heated to approximately 250° F., but shows anoticeable change in the slope of its curve at approximately 200° F.

Immediately following any heating of the panel, frit layer, and theadhesive primer layer to a temperature greater than or equal to theprimer transition temperature, the panel is transported from the heaterand loaded into a mold assembly. In the case of injection molding, themold assembly is closed about the panel. One option available beforeloading the panel is to load any locating or mounting hardware such asstuds, bezels, etc. in the mold cavity so that it will be positionedand/or at least partially encapsulated by the molded gasket as will beseen below. Various ways of loading and locating the mounting hardwarein the molding apparatus are known.

Many thermoplastic materials, such as PVC in general, are eitherhomopolymer or random copolymer in character. Furthermore, suchmaterials have only a single-phase morphology which is poorly suited forthe objectives of the present invention. Melt-processible materialshaving a multi-phase morphology provide the desired characteristics. Themulti-phase morphology of a particular melt-processible material can bedetermined by several techniques including microscopy (e.g., such as byusing a transmission electron microscope) and preferably through the useof dynamic mechanical analysis (DMA), the output of which is bestillustrated graphically by plotting the logarithm of the elastic storagemodulus for a given material along the ordinate versus the temperaturealong the abscissa. An example of a suitable dynamic mechanical analyzeris a DMS-110 available from Seiko Instruments USA, Inc. of Sappington,Mo.

The DMA curve for a melt-processible material having a multi-phasemorphology would approximate that shown in FIG. 7 where the logarithm ofthe elastic storage modulus is plotted against temperature to define thecurve 78 having a glassy region 80 leading to a rubbery region 83exhibiting a rubbery plateau 84, in turn, leading to a viscous flowregion 88. The region 82 between the glassy region 80 and the rubberyregion 83 is marked by the first thermal transition temperature (T₁)where the character of the material changes from a state exhibitingsignificant rigidity to a state exhibiting significant flexibility. Theflexible state is maintained through the rubbery region until the secondthermal transition temperature (T₂) is reached. The second thermaltransition temperature occurs between the rubbery region 83 and theviscous flow region 88, where the character of the material changes froma state exhibiting significant flexibility to a state exhibitingsignificant viscous flow. The second thermal transition temperature isdetermined by a tangent intersection method. In this method, a tangentis drawn along the portion of the curve defining the rubbery region andincluding as many points of the rubbery plateau curve as possible. Asecond line is drawn tangential to the viscous flow region of the curveto intersect the tangent line extending from the plateau. Theintersection point of these two lines defines the second thermaltransition temperature. Ideally, for the vehicular applications of thepresent invention, the first thermal transition temperature would occurbelow 24° C., preferably below 0° C., and most preferably below -20° C.The second thermal transition temperature should occur at a temperaturegreater than 60° C., preferably above 80° C., and most preferably above100° C. Such temperatures provide the desired rubbery plateau over thetypical vehicle operating temperature range of-40° C. to 100° C. Therubbery plateau between the two transition temperatures should encompassa minimum elastic storage modulus greater than 2 million Pascals, andmost preferably greater than 3 million Pascals.

Suitable multi-phase morphology, melt-processible materials generallyinclude block copolymers such as styrene/butadiene/styrene (SBS)elastomers, styrene/ethylene/butadiene/styrene (SEBS) elastomers,copolyester elastomers, polyether block amides, and thermoplasticurethanes. Suitable multi-phase melt-processible materials also includephysical blends and alloys such as polypropylene and EPDM, ofpolyvinylendene chloride and ethylene vinyl acetate, thermoplasticolefins and EPDM, and PVC and nitrile rubber. Another class of suitablemulti-phase melt-processible materials includes multi-phase graftcopolymers such as methacrylate/butadiene/styrene (MBS). Also, blends ofthe above polymers among themselves or with another polymer can also besuitable materials according to this invention.

Examples of multi-phase morphology block copolymers are KRATON™ D (whichis SBS) and KRATON™ G (which is SEBS), both available from ShellChemical Company, Troy, Mich.; HYTREL™ (a copolyester elastomer),available from DuPont Chemical, Wilmington, Del.; PEBAX™ (a polyetherblock amide), available from Elf Atochem North America Incorporated,Philadelphia, Pa.; ELASTOLLAN™ (a thermoplastic urethane), availablefrom BASF, Wyandotte, Mich.; and PELLETHANE™ (a thermoplastic urethane),available from Dow Chemical Company, Midland, Mich.

Examples of physical blends and alloys include SANTOPRENE™ (a blend ofpolypropylene and EPDM), available from Advanced Elastomers, AuburnHills, Mich.; ALCRYN™ (a blend of polyvinyledene chloride and ethylenevinyl acetate), available from DuPont Chemical, Wilmington, Del.;CHEMIGUM™ (a blend of PVC and nitrile rubber), available from GoodyearTire and Rubber Company, Akron, Ohio; VINYPRENE™ (a blend of PVC andethylene terpolymer), available from Vista Chemical Company, Houston,Tex.; 93-X 0401 A-80 (a blend of polypropylene and EPDM), available fromTeknor Apex Company, Pawtucket, R.I.; and SARLINK™ 3000 (a blend ofpolypropylene and EPDM), available from DSM Thermoplastic ElastomersIncorporated, Leominster, Mass.

Such melt-processible materials are distinguishable from gasketingmaterials which are not melt-processible, such as those used in liquidinjection molding processes, i.e., RIM urethanes. This inventionencompasses a method for selecting melt-processible materials forforming gaskets which provide superior adhesion characteristics whensubjected to prolonged periods of both static and dynamic loads.

In contrast, for a typical single-phase morphology material, such asVISTA™ brand 484.51 plasticized PVC, available from Vista PerformancePolymers of Jeffersontown, Ky., the DMA graph (FIG. 8) is a curve 71lacking a well-defined rubbery plateau, as indicated by the steadilydeclining curve portion 76 between the glassy region indicated byportion 72 and the viscous flow region indicated by curve portion 74.Such a curve is characteristic of a material having a single thermaltransition temperature (T₁) but lacking, within the range of automotiveinterest between about -50° C. to about +150° C., a second transitiontemperature (T₂) as described above. The single thermal transitiontemperature is established by the location of a peak 73 on a curve 75formed from a plot of Tan δ versus temperature. Tan δ is defined as theratio of E" to E', where E' is the elastic storage modulus and E" is theloss modulus of the material. If there is more than one peak in Tan δversus Twithin the first transition region, the most prominent peakestablishes the thermal transition temperature.

Alternatively, it may be desirable to use melt-processible materialsthat are cross-linkable such as by vulcanization. Cross-linking can beachieved by incorporating reactable sites in the melt-processiblepolymer backbone of the polymer formulation and/or by adding reactablemoieties to the polymer formulation itself which are thereafterincorporated into the molded gasket network during the cure phase of themolding process itself. Reactable sites incorporated in the polymerbackbone are commonly in the form of unsaturation and are incorporatedduring polymerization of the starting monomers of the polymer by addingmonomers containing multiple sites of unsaturation such as butadiene,isoprene, dicyclopentadiene, ethylidene norbornene, hexadiene, etc.Examples of cross-linking means that are reactable moieties added to thepolymer formulation include peroxides such as dicumyl peroxide.

Examples of melt-processible gasketing material with a cross-linkedstructure formed from formulations with unsaturation in the polymerbackbone are styrene butadiene rubber (SBR) elastomer and ethylenepropylene diene terpolymer (EPDM) elastomer. Cross-linking between sitesof unsaturation on adjacent polymer chains is achieved preferably viasulfur vulcanization as is commonly known. An example of a gasketingmaterial formed from a formulation that is a peroxide cross-linkablesystem is ethylene propylene copolymer (EPM) elastomer.

In such cross-linkable melt-processible materials it is further desiredthat during the formng process, the molding material does not cross-linkappreciably in its melt phase (such as within the barrel of an injectionmolding apparatus), but once injected into the mold and filling the moldcavity, cross-links quickly, such as by vulcanization, to form thegasket. To achieve this in an injection molding process, the temperatureof the cross-linkable material in the injection barrel is maintained ata relatively low temperature of around 100° C. to 120° C. such that thecross-linkable melt-processible material does not gel in the barrel. Bycontrast, the mold temperature is maintained around 150° C. to 220° C.(preferably, around 180° C. to 200° C.) so that as soon as the materialfills the mold cavity, but not appreciably before, it cross-links totake the form of the cavity. Once cross-linking is substantiallyunderway within the filled mold cavity, it is further desirable that thecuring time in the mold cavity be short, between 1 and 8 minutes(preferably between 1 and 5 minutes, and most preferably between 1 and 3minutes) so as to minimize residence time within the mold. Longer curingresidence time within the mold can make the cycle time undesirably long,thus adding cost to the finished window assembly.

MOLD APPARATUS

To reduce the cycle time per molded part, it is conventional in the artto use multiple side-by-side cavity molds. For example, a doubleside-by-side cavity mold 90 can be used (FIG. 18) for producing modularwindows. From the force diagram, it can be seen that a doubleside-by-side cavity mold 90 would require twice the clamp tonnage neededfor a single cavity mold 92 (FIG. 17) to keep it closed during theinjection cycle. This increased clamp tonnage can be a disadvantage,especially for large-sized windows (such as the type described inExample 1) that are used as side and rear windows on automobiles,minivans, light trucks, and the like, which may require clamp tonnagesin excess of 1,500 tons for a double side-by-side cavity mold 90. Suchlarge hydraulic clamp tonnage presses are expensive. In addition tothis, the sheer size of such automobile windows could require overlylarge plate sizes and associated plates for a multiple side-by-sidecavity mold which could require custom fabrication, extra floor space,and disadvantageous cost.

To overcome these disadvantages, a novel stacked-cavity molding conceptto produce large area modular windows is schematically shown in FIG. 19.The novel stacked-cavity mold 100 for molding modular window assembliesovercomes the deficiencies of the conventional side-by-side cavity mold90 shown in FIG. 18. Mold 100 can receive multiple panels of glass 16a,16b without being larger in lateral dimension. By doing so, theeffective size of the mold plates 102a, 102b, and 102c remain the sameas the conventional single cavity mold 92 shown in FIG. 17. Also acomparison of the force diagrams in FIGS. 17, 18, and 19 reveals thatthe total clamp tonnage needed for the stacked-cavity mold design 100will be substantially equal to the clamp tonnage needed for the singlecavity mold 92 in FIG. 17 and about half that of the side-by-side cavitymold arrangement 90 in FIG. 18.

The stacked-cavity mold configuration 100 of FIG. 19 includes lower,middle, and upper plates 102a, 102b, and 102c, respectively separatedfrom each other by lower and upper parting lines 104a, 104b,respectively. Lower plate 102a includes a cavity 106 formed in its uppersurface 108 to receive a panel of glass 16a or other panel-likematerial. Although cavity 106 is shown as being relatively planar, thisis by way of example only and may be configured to accept any desiredcurved or shaped panel. It is specifically contemplated that cavity 106may be configured to receive a curved sheet of glass or other materialfor use as a vehicle window. In the embodiment shown, upper plate 102cmay be a mirror image of plate 102a, such that a mold cavity 110 isdefined in a lower surface 112 of plate 102c and configured to receive asheet of glass 16b therein. Disposed between plates 102a and 102c ismiddle plate 102b having a lower and upper surfaces 114a, 114brespectively configured to engage and seal with surfaces 108 and 112,respectively, when clamped together as shown. For window encapsulations,middle plate 102b may include mirror image mold cavities 116a, 116bdefined in surfaces 114a, 114b respectively shaped to form the desiredgasket profile. Alternatively, two different modular window assembliescan be molded in tandem using the stacked-cavity molding apparatus ofthis embodiment. This is particularly useful when molding left-hand sidewindows and right-hand side windows for vehicles where the left- and theright-window assemblies, though generally similar, are not symmetric.Molding in tandem, such as in the stacked-cavity mold of FIG. 19,enables fabrication of both window assemblies of the set with a moldingcycle time per part approximately half the conventional cycle time perpart where the conventional single-cavity mold of FIG. 17 be used.Moreover, the tandem molding of the left-side/right-side modular windowset facilitates ease of inventory and stock control within amanufacturing plant. In the embodiment shown in FIG. 19, cavities 116a,116b produce a gasket profile similar to gasket 26 shown in FIG. 2. Eachof the mold cavities 116a, 116b are in fluid communication through aseries of runners 118 with a sprue 120 which, in turn, receives a nozzle(not shown) of a conventional plastic injection machine. Preferably,sprue 120 and runners are centrally located and configured within middleplate 102b so that the melt-processible material is injected intocavities 116a, 116b uniformly.

The vertical configuration of the stacked-cavity mold 100 has thefurther advantage that panels 16a and 16b are gravity-supported onplates 102a and 102b, respectively, with consequent ease of loading andalignment without need for vacuum assists and the like. Similarly, studs119a and 119b can be gravity-supported when loaded into the mold cavityprior to injection molding. Suitable support means such as magneticretention, clamping, vacuum assist, and their like can be used tosecure, position, and align studs 119c and 119d in the mold cavity priorto injection molding of the melt-processible material.

FIG. 20 shows an alternate embodiment of stacked-cavity mold 200incorporating a third parting line 204c, splitting the middle plate intotwo components shown here as 202b, 202c. Provision of parting line 204cfacilitates removal of the runner 218 and sprue 220 after each cycle.Additionally, the lower and upper plates 202a, 202d, respectively, havebeen configured along surfaces 208 and 212 to form mold cavities 217a,217b, which cooperate with mold cavities 216a, 216b, respectively, toform a three-sided encapsulation about the peripheral edge of glasspanels 16a, 16b. To locate each glass sheet 16a, 16b with respect toeach mold cavity assembly such as 216a, 217a, the cavity 206, 210 toreceive each sheet of glass may be defined in one or both of the platessuch as 202a, 202b. As shown in FIG. 20, cavities 206, 210 areconfigured in the lower surface 214a of plate 202b, and the uppersurface 214b of plate 202c.

Yet another embodiment of a stacked-cavity mold 300 is shown in FIG. 21.In this configuration, a top and bottom platen 302, 304 respectively areinterconnected by at least two tie rods 306. One platen (such as 302)moves along tie rods 306 with respect to the other platen (304) as iswell-known in press machinery and the like. A lower mold plate 308 isdisposed on an upper surface 310 of platen 304 and itself having anupper surface 312 configured to cooperate and seal with a lower surface314 of a middle plate 316 to accommodate a sheet of glass 16a and formthe mold cavity 318a along one surface or about the peripheral edge ofthe glass. Middle plate 316 is, in turn, suspended by guide pins 320slidably retained by bushings 322 in cylindrical holes 324 defined in anupper plate 326. Upper plate 326 is mounted to the lower surface 328 oftop platen 302. Upper plate 326 also has a lower surface 330 whichcooperates with an upper surface 332 of middle plate 316 to accommodatea sheet of glass 16b, and form the mold cavity 318b adjacent the glasssurface and/or edge. As in the previous embodiments, glass panels 16a,16b may be located in the mold using conventional locating pins,springs, or the like.

The stacked-cavity mold design, such as shown in FIGS. 19-20, isparticularly useful for cross-linkable melt-processible material whichtypically requires a longer cycle time due to the cross-linking step inthe mold. For such materials, the stacked-mold configuration of thisinvention greatly enhances productivity and economic manufacturing. Forexample, a stacked-cavity mold will potentially reduce the cycle timeper molded part by almost one-half compared to a single cavity mold.

The opening and closing to insert and remove the glass can beaccomplished in several ways. Referring to FIG. 21, middle plate 316 canbe attached to either the top or the bottom plates 326, 308 and can beguided by guide pins, hydraulic cylinders, or the like 320.Alternatively, a hinge mechanism such as a scissors mechanism (notshown) can also be used with the top or the bottom plate 326, 308 tocontrol the movement of the middle plate 316. It is preferred thatmiddle plate 316 is attached to the top plate 326. FIG. 21 shows thatmiddle plate 316 is attached to the top plate 326 using suitably longguide pins 320. In this configuration, upon opening the mold 300, middleplate 316 will separate from top plate 326 under its own weight. FIG. 22shows an example of a stacked-cavity molding process. When at the fullyopen mold position, multiple glass panels 16a, 16b and other accessoriesare mounted in the stackedcavity mold. Following that, mold 300 closesand the melt-processible gasketing material is injected into the moldcavities 318a, 318b. Upon filling of the mold and substantial completionof any cross-linking reactions in the gasketing material, the mold isopened. The partially open position of FIG. 22c illustrates that uponmold opening, the first separation takes place between the top plate 326and the middle plate 316 until complete separation is attained. Afterthat, and upon further movement of the top platen 302, separationbetween middle plate 316 and bottom plate 308 starts and continues untilthe mold is fully open. The molded window assemblies 16a, 16b are thenremoved from the stacked-cavity mold which is then ready for another setof glass panels and accessories in a new cycle. This type of moldopening and closing mechanism is uncomplex and economical.

Plates 308, 316, and 326 can be made of the same or different materials.Suitable materials include tool steel and composites such as filledepoxy. When molding cross-linkable polymer formulations, such as duringformation of EPDM gaskets, it is desirable that the mold be heated, suchas to 150° C. to 220° C. or thereabouts. In this regard, it may bedesirable to use plate materials, and especially, for economy, a middleplate material, that has a high thermal conductivity. Preferably, aplate material is selected that has a thermal conductivity, as heated inthe mold, greater than about 80 watts/metre.K, and more preferablygreater than about 100 watts/metre.K, and most preferably greater thanabout 120 watts/metre.K. Suitable materials include copper alloys suchas copper-beryllium alloy, aluminum, aluminum alloys, and their like.

Such a stacked-cavity mold configuration is suitable to produce anylarge area flush glazing windows. Further, such stacked-cavity moldconfiguration is also useful to produce three-sided encapsulation windowassemblies and especially when molding in cross-linkable,melt-processible materials such as EPDM, SBR, and their like.

The stacked-cavity mold configurations shown in FIGS. 19-22 illustratemold opening and closing in the vertical direction. Similarstacked-cavity mold configuration can also be used, with appropriatemodifications, for a horizontal molding operation to fabricate modularwindows where mold opening and closing will be in the horizontaldirection.

To demonstrate the effectiveness of the method of selecting theappropriate material for forming the gaskets according to thisinvention, several window panel assemblies were manufactured usingmelt-processible materials exhibiting a multi-phase morphology, or thatare cross-linkable, and selected from the materials described above.

EXAMPLE 1

A window panel assembly suitable for use as a fixed rear side window ona commercial minivan vehicle, and attached to the vehicle similar tothat shown in FIG. 2, included a PVC gasket injection molded directly tothe window panel, and a plurality of fasteners in the form of studspartially encapsulated by the PVC and floating therein with respect tothe glass surface of the panel. Prior to loading into a conventionalsingle-cavity mold, such as is shown in FIG. 17, the glass panel, whichwas coated around its perimeter with a ceramic frit blackout layerwhich, in turn, was primed with A-57 acrylic primer, was preheated toabout 325° F. The PVC compound was the VISTA™ brand 484.51 availablefrom Vista Performance Polymers, in Jeffersontown, Ky. The gasket had awidth approximately equal to 0.5 inch and a thickness of approximately0.375 inch, and extended around the entire peripheral edge of the panelover a ceramic blackout frit. The glass panel was about 0.15 inch thickby about 24 inches wide and about 39 inches long and was tempered and ofcompound curvature. Analysis of the gasket material was conducted on aDMS-110 instrument made by Seiko Instruments U.S.A., Inc. of Sappington,Mo., at a heating rate of 10° C. per minute and a fixed frequency of 1hertz (Hz). The resulting curve shown in FIG. 8 exhibits no rubberyplateau as defined above and only a single thermal transitiontemperature occurring at about 30° C. as exhibited by curve 75. Thewindow panel assembly was mounted in a vehicle window opening with thefasteners floating in the encapsulant tightened to 25 inch pounds oftorque load and exposed to a temperature of 80° C. for 200 hours.Localized adhesive failure occurred between the single-phase morphologygasket and glass panel underneath many of the mechanical fasteners.

EXAMPLE 2

A gasket of the same dimension as described above and shown in FIG. 2was injection molded directly to a window panel of similar size usingELASTOLLAN™ SP-806 thermoplastic urethane available from BASF. Prior tomolding of the gasket onto the panel, the panel was prepared by primingthe surface of frit layer 25 on surface 18 with a wipe of A-57 primerbased on acrylics with additional coupling agents available from theDonnelly Corporation of Holland, Mich., followed by an overcoat wipe ofAP-134 primer, a solution of silane coupling agents in a low-boilingorganic solvent available from the Lord Corp. of Erie, Pa. Afterformation of the gasket, the window panel was installed on a vehiclewindow frame with the fasteners tightened to 25 inch pounds of torqueload and subjected to an 80° C. temperature for more than 200 hours. Theintegrity of the bond between the multi-phase morphology gasket and theglass panel underneath the mechanical fasteners was substantiallypreserved after such testing.

EXAMPLE 3

A gasket, substantially similar to that shown in FIG. 2 and having asize as indicated in Example 1, was injection molded to a window panelof similar size using PEBAX™ brand 3533 polyether block amide availablefrom Elf Atochem North America, Inc. of Philadelphia, Pa. Prior toreceiving the gasket, the window panel was primed with a wipe ofBETASEAL™ brand 435.18 coupling agent solution, which, in turn, wasovercoated with a wipe of BETASEAL™ brand 435.20A urethane-based primer,both available from Essex Chemical Corp. of Sayerville, N.J. Afterformation of the gasket, the window panel was mounted in a vehicle doorframe using the attachment members which were tightened to 25 inchpounds of torque. The window panel assembly was then subjected totemperatures of 80° C. for more than 200 hours. The integrity of thebond between the multi-phase morphology gasket and the glass panelunderneath the mechanical fasteners was substantially preserved aftersuch testing.

EXAMPLE 4

A gasket generally the size as described in Example 1, but attached to a12 by 12 flat, tempered, frit-coated glass substrate and similar to thatshown in FIG. 2, was made from SANTOPRENE™ brand 111.73 melt-processibleEPDM/polypropylene blend material, by injection molding onto the glasspanel which was primed using a wipe of BETASEAL™ brand 435.18 silanecoupling agent overcoated with CHEMLOK™ brand 487 primers, availablefrom Lord Corp. Prior to loading into the mold of the injection-moldingapparatus, the primed panel was preheated to about 275° F. The windowpanel was mounted to a simulated door frame section using the studattachment members floating within the gasket tightened to 25 inchpounds of torque. The window panel assembly was then subjected to 80° C.heat for more than 200 hours. The integrity of the bond between themulti-phase morphology gasket and the glass panel underneath themechanical fasteners was substantially preserved after such testing.

EXAMPLE 5

A gasket, substantially identical to that shown in FIG. 2, was injectionmolded from ELASTOLLAN™ brand SP-806 thermoplastic urethane from BASFdirectly onto a glass panel. The dimensions of the gasket and panel weresimilar to those in Example 1. Prior to receiving the gasket, the windowpanel was primed using a wipe of BETASEAL™ brand 435.18 primer followedby an overcoat wipe of BETASEAL™ brand 435.20A primer. Following moldingof the gasket onto the panel, a 40 pound weight was suspended from oneof the attachment members encapsulated within the gasket. The entireassembly was then subjected to temperatures of 80° C. for more than 200hours. The integrity of the bond between the multi-phase morphologygasket and the glass panel underneath the mechanical fasteners wassubstantially preserved after such testing.

EXAMPLE 6

A melt-processible, cross-linkable gasketing material utilizing ethylenepropylene diene terpolymer (EPDM) elastomer supplied under the tradename WT-2321 (550-6171) from Burton Rubber Processing Incorporated,Burton, Ohio, was compression molded to a glass panel for 15 minutescompression at 380° F. to form a roughly 1 inch wide by about 1/8 inchthick gasket. Prior to molding, the panel was prepared by priming thefrit overcoated glass surface with a wipe of AP-134 primer followed byanother wipe (as an overcoat) of primer CHEMLOK™ 250, both availablefrom the Lord Corporation, Pennsylvania. Following molding of the EPDMgasket onto the panel, an 8 pound weight was suspended from the 1 inchwide molded EPDM gasket in a 90° T-peal configuration. The entireassembly was then subjected to a temperature of 80° C. for more than 300hours. The integrity of the bond between the EPDM gasket and the glasspanel was preserved at the end of the test period.

Furthermore, the tensile creep data for the EPDM material, at threedifferent temperatures (60° C., 80° C., and 100° C.), was measured andis shown in FIG. 16. This indicates that the melt-processiblecross-linkable EPDM material is not susceptible to tensile creep strainto any great extent, that the creep behavior does not change appreciablywith increase in temperature and that EPDM achieves the objectives ofthe present invention.

EXAMPLE 7

A window panel assembly similar to that shown in FIG. 2 and suitable touse as a fixed side window on a commercial minivan was produced byinjection molding PELLETHANE™ brand 2103-80AE thermoplastic urethane(TPU) available from Dow Chemical Company, Midland, Mich. Prior tomolding, the TPU was dried, per manufacturer's processingrecommendation, to assure a moisture content of less than about 0.02percent or thereabouts. The molding equipment used was a conventional700 ton vertical press and was equipped with a single-cavity mold, asschematically shown in FIG. 17. The glass panel for the window assemblywas obtained from Acustar Incorporated, McGraw Glass Division, Detroit,Mich. The glass panel was about 24 inches wide, about 39 inches long,and about 0.15 inch thick tempered soda-lime float glass and of acompound curvature. A black ceramic frit blackout layer of roughlybetween 2 to 4 inches width was also present around the perimeter on theinside (concave) surface of the glass panel. Prior to molding the gasketthereto, the portion of the black frit layer intended to receive thegasket was primed with a wipe of BETASEAL™ brand 435.18 silane solutionfollowed by another wipe (in an overcoat fashion) of BETASEAL™ brand435.20A urethane based primer, both available from Essex SpecialtyProducts Incorporated, Troy, Mich. The primed glass panel was heated toa temperature of roughly about 325° F. using infrared heaters and wasplaced into the injection mold. Prior to the placement of the glasspanel, 10 metal studs having a rectangular anchor or base of roughly 3/4inch by 3/8 inch dimension with a cylindrical shoulder and with about1/2 inch long threaded shaft projecting from the base were mounted inthe mold cavity. The studs were located in the mold such that they wereabout 8 to 12 inches apart from each other. The thermoplastic urethanematerial was then injected into the single-cavity mold forming thegasket and encapsulating the base and up to the upper rim of theshoulder of all the studs. The studs thus molded had their anchor/basespaced from the glass panel such that the stud floated with respect tothe panel, such as is shown schematically in FIG. 2. After completion offormation of the gasket in the mold, the mold was opened and the moldedwindow assembly was removed.

The molded window assemblies were mounted to a simulated minivan vehicledoor frame using nuts fastened onto the shafts of the mounting studsembedded in the window gasket. The nuts were tightened to 20 to 30 inchpounds of torque. Such molded window assemblies were subjected totesting appropriate for their intended use in a vehicle. These testsincluded prolonged heat aging (such as at 80° C. for 300 hours), coldtesting (such as storage at -30° F.), exposure to high humidity atelevated temperature, water soak (such as at 80° C. for in excess of 200hours), thermal cycling, hot/cold vibration, and UV resilience testingin a Xenon weatherometer (SAE J1960, 2500KJ). Upon completion of thevarious tests, the integrity of the bond between the glass panel and thegasket underneath the studs remained intact. The windows of this examplewere found to be suitable for use on a vehicle under dynamic andlong-term static loads.

Samples of the gasketing materials described above were further analyzedusing the dynamic mechanical analysis device described earlier. Thesamples formed according to Examples 2-5 displayed curves characteristicof multi-phase morphology and exhibited characteristics indicative oftwo thermal transition temperatures as opposed to the PVC of Example 1,which exhibited the single-phas e morphology curve seen in FIG. 8. Shownin FIGS. 9-12 are DMA curves of the logarithm of the elastic storagemodulus plotted against temperature for each separate material used inExamples 2-5. Following the dynamic mechanical analysis, each of thematerials were tested using the American Society of Testing MaterialsStandards protocol for tensile creep. The testing standards are set outin detail in ASTM Designation D 2990-91 approved Nov. 15, 1991, andpublished by ASTM in January 1992, the contents of which areincorporated herein by reference.

Referring to FIG. 9, curve 100 is a plot of the logarithm of the elasticstorage modulus for ELASTOLLAN™ brand SP-806 thermoplastic urethaneversus temperature, while curve 102 is a plot of Tan δ (i.e., TAN DELTA)against temperature. Using the above method, the lower thermaltransition (T₁) is established by the peak (P₁) of curve 102 whichindicates the transition between the glassy region and rubbery region ofthe material and occurs at about -7° C. This point also establishes thelower extent of the region encompassed by the rubbery plateau. Thehigher thermal transition temperature (T₂) is established by the tangentintersection method and occurs at approximately 144° C. and designatedP₂. Point P₂ defines the uppermost extent of the region encompassed bythe rubbery plateau of curve 100.

FIG. 10 illustrates a similar plot for HYTREL™ HTR brand 8122 blockcopolymer material. In this example, the lower thermal transitiontemperature T₁ occurs below -50° C. at about -58° C. marked by peak P₁in curve 106 (Tan δ versus temperature) and indicating the lower extentof the reaion encompassed by the rubbery plateau o n DMA curve 104. Theupper thermal transition temperature T₂ occurs above 125° C. at about134° C. marked by point P₂ established by the tangent intersectiontechnique.

The logarithm of the elastic storage modulus (log E') versus temperature(Celsius) and Tan δ curves, 108, 110, respectively, for PEBAX™ brand3533 block copolymer material are shown in FIG. 11. Note that, incontrast to the previous two examples, the Tan δ curve 110 does notdisplay a prominent P₁ at the lower thermal transition temperature T₁.The location of this lower transition temperature is preferablydetermined numerically by data, although a visual approach could beused. In this instance, the PEBAX™ brand 3533 polymer has a lowerthermal transition temperature at -54° C. Using the tangent intersectionmethod, the upper thermal transition temperature T₂ marked by point P₂occurs at about 132° C.

In contrast, SANTOPRENE™ brand 111.73 polymeric alloy illustrates awell-defined Tan δ curve 112 (FIG. 12) containing more than one peak.Following the technique outined above, the most prominent peak P₁ marksthe lower thermal transition temperature T₁ at approximately -47° C.,the lower extent of the region encompassed by the rubbery plateau on DMAcurve 114. The upper extent of the region encompassed by the rubberyplateau and the second thermal transition temperature T₂ occurs at 150°C., at the intersection P₂ of the tangents from the rubbery plateau andthe viscous flow region of the curve 114.

T he result of tests for creep strain are shown in FIGS. 13-15 wherepercent of creep strain is plotted against time in hours on alogarithmic scale at differing temperatures; namely, 60° C., 80° C., and100° C. and at a stress of about 85 psi. The curve identified by the design ation VISTA™ 85 (VISTA™ brand 484.51) is the curve for a typicalsingle-phase morphology PVC material. The steep slope of the VISTA™curve indicates that this single-phase melt-processible material issusceptible to excessive creep under load--especially at elevatedtemperatures. The other curves represent the tensile creep for theSANTOPRENE™, ELASTOLLAN™ (TPU), PEBAX™, and HYTREL™ (HYTREL™ brand HTR8122) materials identified above. The comparison of the curves clearlyshows that single-phase morphology materials are more susceptible tocreep strain than multi-phase morphology materials as selected accordingto this invention, and particularly at elevated temperatures. Ingeneral, to achieve the objectives of this present invention, it isdesirable that the melt-processible material be selected so that, whentested as described above and at a stress of about 85 psi, the creep ofthe material at 100° C. is below about 50 percent creep strain.

A plot of the elastic storage modulus versus temperature for fivematerials, VISTA™ brand 484.51 (curve 201), SANTROPRENE™ brand 117-73(curve 202), PEBAX™ brand 3533 (curve 203), HYTREL™ brand HTR 8122(curve 204), and ELASTOLLAN™ brand SP806 (curve 205) used in theexamples and creep studies is shown in FIG. 24. The rubbery plateauexhibited by the four multi-phase materials (SANTROPRENE™ brand 111-73,PEBAX™ brand 3533, HYTREL™ brand HTR 8122, and ELASTOLLAN™ brand SP806)is clearly evident and commences roughly between line L1 at about 30° C.and at an elastic storage modulus of about 50 million Pascals, and lineL2 at about 120° C. and at an elastic storage modulus of about 10million Pascals.

By contrast, curve 201 of the single-phase VISTA™ brand 484.51plasticized PVC material fails to exhibit a rubbery plateau within thetemperature range of automotive interest (between about -50° C. to about+150° C.) but, rather, exhibits a steep, steady decline in modulusdropping from about 3 billion Pascals at about -40° C. to below 1million Pascals at about +140° C. without exhibiting a rubbery plateauwithin the temperature range of automotive interest.

From the above description, a method is provided for selectingmelt-processible materials for use in manufacturing gasketed vehiclewindow panel assemblies offering long-term bonding of the window panelto the vehicle. This method includes the steps of measuring an elasticstorage modulus of the melt-processible material as a function oftemperature; plotting the data points gathered from the step ofmeasuring to produce a first curve; and determining whether the firstcurve produced by the data point displays a glassy region, a rubberyregion exhibiting a rubber plateau, and a viscous flow region. From theplot, the method includes selecting a first thermal transitiontemperature for the gasket material, preferably established by the mostprominent peak of a second curve that plots the ratio of the lossmodulus of the material to the elastic storage modulus of the materialversus temperature. Following the selection of the first thermaltransition temperature, a second thermal transition temperature isestablished by a first line tangential to the rubbery plateau of thefirst curve, and a second line intersecting with the first line,tangential to the viscous flow region of the second curve. The secondthermal transition temperature is identified by the intersection of thefirst and second lines.

The above description also provides a method for manufacturing a windowpanel assembly, which comprises the steps of providing a window panelhaving a peripheral edge, selecting a melt-processible material having amulti-phase morphology, and forming the gasket on at least one surfaceof the window panel from the melt-processible material selected along ornear the peripheral edge. The method further includes the step oflocating an attachment member in the gasket and spacing said attachmentmember from the window panel. In addition to the steps outlined above,the method further contemplates applying an adhesion-promoting compoundto at least one surface of the window panel or to a frit layer of thepanel. The step of selecting the melt-processible material includesselecting from the group of polymers consisting essentially of blockcopolymers, physical blends and alloys, two-phase graft copolymers, andblends thereof with each other. The step of selecting themelt-processible material further includes the step of selecting thematerial from a group of polymers having a glassy phase, a rubberyplateau, and a viscous flow phase.

The invention results in a vehicle window panel assembly including awindow panel having a gasket attached to at least one surface of thewindow panel with the gasket formed from a melt-processible materialhaving a multi-phase morphology. The melt-processible material used toform the gasket further exhibits characteristics displaying a rubberyplateau bounded by a glassy region and a viscous flow region, anddisposed between thermal transition temperature points. In a preferredembodiment of the vehicle panel assembly, the gasket material has afirst thermal transition temperature less than 24° C., preferably lessthan 0° C., and most preferably less than -20° C. The second thermaltransition temperature is greater than 60° C., preferably greater than80° C., and most preferably greater than 100° C. The melt-processiblematerials having these thermal transition temperatures are preferablyselected from a group of polymers consisting essentially of blockcopolymers, physical blends and alloys, multi-phase graft copolymers,and blends of the above with each other or with other polymers where theresultant blend achieves the objectives of the present invention. Thevehicle window panel assembly further preferably includes a frit layerbonded to at least one surface of the window panel between the windowpanel and the gasket. Furthermore, an adhesion-promoting compound may bedeposited between the gasket and the frit layer or between the gasketand the one surface of the window panel receiving the gasket. Mountedwithin the gasket member and extending therefrom are one or moreattachment members for mounting the window panel assembly in thevehicle. Such attachment members include a fastener having a baseportion encapsulated in a gasket and a shaft portion extending from thegasket for engaging the vehicle. Such attachment members include a studhaving a head portion at least partially surrounded by the gasketmaterial and a shaft extending from the head and out the gasket toengage the vehicle. The head of the stud is preferably spaced from thewindow panel by the gasket material. As an alternate to at leastpartially encapsulating the head portion of the stud, this head portioncan be directly adhered to the gasket material using a suitable adhesivesuch as a urethane, acrylic, silicone, or epoxy adhesive.

Using the method of selecting the gasket materials according to thisinvention, and manufacturing single-, two-, or three-sidedencapsulations on the window using such selected materials, a modularwindow assembly is produced which is better suited for the wide-range ofenvironments that the vehicle encounters over its useful life with asignificantly reduced risk of a failure in the gasket assembly bondingthe window panel to the vehicle. By selecting gasket materials accordingto the method and teachings described herein, single-, two-, orthree-sided gasketed window panels can be secured in the window openingusing attachment members without deteriorating the bond between theGasket member and the window panel assembly. Such seletion results in animproved window panel assembly capable of withstanding prolonged dynamicand static loads without a failure of the bond, and with secureretention of any attachment member, such as a stud, partiallyencapsulated by and floating in the gasket. The prolonged life of thewindow panel assembly results in a substantial saving to the vehicleowner as well as reduced repair costs to the manufacturer resulting fromwarranty work. Such improved modular window panel assemblies are usefulin a variety of vehicles and especially for large area windows, andparticularly for large area flush-mounted glazings, such as are used asfront, rear, and side windows, and as sunroofs, in automobiles,minivans, vans, trucks, and busses and which utilize a window panel thatweighs at least about 3 kilograms (with a window panel weight of atleast 5 kilograms common for front and rear windows, and for sidewindows on minivans and larger vehicles) and with a window panel area ofat least about 350 square inches.

The above description is considered that of the preferred embodimentsonly. Modification of the invention will occur to those skilled in theart and to those who make and use the invention. Therefore, it isunderstood that the embodiments shown in the drawings and describedabove are merely for illustrative purposes and are not intended to limitthe scope of the invention, which is defined by the following claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A method formanufacturing a vehicle window panel assembly, comprising the stepsof:providing a window panel having a peripheral edge; selecting amelt-processible, polymeric material which has a multi-phase morphology,is resistant to tensile creep, and has a glassy phase, a rubberyplateau, a viscous flow phase, a first transition temperature betweensaid glassy phase and said rubbery plateau, and a second transitiontemperature between said rubbery plateau and said viscous flow phase;and forming and adhering a gasket on at least one surface of said windowpanel from said melt-processible material; providing an attachmentmember for securing said vehicle window panel assembly to a vehiclebody; embedding a first portion of said attachment member in said gasketduring formation of said gasket such that a second portion of saidattachment member extends from said gasket for securement to the vehiclebody, whereby said gasket is securely bonded to said one surface of saidwindow panel and said melt-processible polymeric material resists creepwhen said window panel is attached to a vehicle with said attachmentmember.
 2. The method as defined in claim 1, further including the stepof locating said attachment member in a gasket forming cavity of a moldapparatus such that said first portion of said attachment member isspaced from said window panel while said second portion of saidattachment member extends out of said cavity.
 3. The method defined inclaim 2, wherein the step of selecting said melt-processible materialincludes the step of selecting a polymer from the group consistingessentially of a styrene/butadiene/styrene elastomer, astyrene/ethylene/butadiene/styrene elastomer, a copolyester elastomer, apolyether block amide, a thermoplastic urethane, amethacrylate/butadiene/styrene elastomer, a polypropylene/EPDM blend, apolyvinyledene chloride/ethylene vinyl acetate blend, a PVC/ethyleneterpolymer blend, and a PVC/nitrile rubber blend.
 4. The method asdefined in claim 3, wherein the step of selecting said polymer materialincludes selecting one of said thermoplastic urethane, said polyetherblock amide, said polypropylene/EPDM blend, and said copolyesterelastomer.
 5. The method as defined in claim 4, wherein the step ofselecting said polymer material includes selecting said thermoplasticurethane.
 6. The method as defined in claim 4, wherein the step ofselecting said polymer material includes selecting said polyether blockamide.
 7. The method as defined in claim 4, wherein the step ofselecting said polymer material includes selecting saidpolypropylene/EPDM blend.
 8. The method as defined in claim 2, whereinthe vehicle includes one of an automobile, a minivan, a van, a truck,and a bus.
 9. The method as defined in claim 8, wherein the step ofproviding said window panel includes providing at least one of a sidewindow, a front window, a sunroof, and a rear window of the vehicle. 10.The method as defined in claim 9, wherein the step of providing saidwindow panel includes providing said window panel with a weight of atleast about 3 kilograms and an area of at least about 350 square inches.11. The method as defined in claim 2, further including the step ofapplying an adhesion-promoting compound to said at least one surface ofsaid window panel and forming said gasket on said adhesion promotingcompound.
 12. The method as defined in claim 2 including providing saidwindow panel with a frit layer on said at least one surface of saidwindow panel and forming said gasket on said frit layer.
 13. The methodas defined in claim 2, wherein said window panel is one of a sidewindow, a front window, a rear window, and a sunroof of one of anautomobile, a minivan, a van, a truck, and a bus.
 14. The method asdefined in claim 13, wherein said window panel has a weight of at least3 kilograms and an area of at least about 350 square inches.
 15. Aproduct made according to the method as defined in claim
 1. 16. Themethod as defined in claim 1, wherein the step of selecting saidmelt-processible material includes selecting from a group of polymersconsisting essentially of: block copolymers, physical blends and alloys,two-phase graft copolymers, and blends thereof with each other.
 17. Themethod as defined in claim 16, wherein the step of selecting saidmelt-processible material includes selecting from the group consistingessentially of one of a styrene/butadiene/styrene elastomer, astyrene/ethylene/butadiene/styrene elastomer, a copolyester elastomer, apolyether block amide, a thermoplastic urethane, amethacrylate/butadiene/styrene elastomer, a polypropylene/EPDM blend, apolyvinyledene chloride/ethylene vinyl acetate blend, a PVC/ethyleneterpolymer blend, and a PVC/nitrile rubber blend.
 18. The method asdefined in claim 16, wherein the step of selecting said melt-processiblematerial includes selecting one of a thermoplastic urethane, a polyetherblock amide, a polypropylene/EPDM blend, and a copolyester.
 19. Themethod as defined in claim 16, wherein the step of selecting saidmelt-processible material includes selecting a thermoplastic urethane.20. The method as defined in claim 16, wherein the step of selectingsaid melt-processible material includes selecting a polyether blockamide.
 21. The method as defined in claim 16, wherein the step ofselecting said melt-processible material includes selecting apolypropylene/EPDM blend.
 22. The method as defined in claim 1, whereinsaid first thermal transition temperature is less than 24° C.
 23. Themethod as defined in claim 22, wherein said second thermal transitiontemperature is greater than 60° C.
 24. A method for manufacturing avehicle window panel assembly, comprising the steps of:providing awindow panel; selecting a melt-processible, polymeric material which hasa multi-phase morphology, is resistant to tensile creep, and has aglassy phase, a rubbery plateau, a viscous flow phase, a firsttransition temperature between said glassy phase and said rubberyplateau, and a second transition temperature between said rubberyplateau and said viscous flow phase; forming and adhering a gasket on atleast one surface of said window panel from said melt-processiblematerial; providing an attachment member for securing said vehiclewindow panel assembly to a vehicle body; embedding a portion of saidattachment member in said gasket during formation of said gasket suchthat said attachment member portion is spaced from said surface of saidwindow panel while another portion of said attachment member extendsfrom said gasket for securement to the vehicle body, whereby said gasketis securely bonded to said one surface of said window panel and saidmelt-processible polymeric material resists creep when said window panelis attached to a vehicle with said attachment member.
 25. A product madeaccording to the method as defined in claim
 24. 26. A method formanufacturing a vehicle window panel assembly, comprising the stepsof:providing a window panel; selecting a melt-processible, polymericmaterial which has a multi-phase morphology, is resistant to tensilecreep, and has a glassy phase, a rubbery plateau, a viscous flow phase,a first transition temperature between said glassy phase and saidrubbery plateau, and a second transition temperature between saidrubbery plateau and said viscous flow phase; said step of selecting saidmelt-processible polymeric material including selecting said materialfrom a group of polymers consisting of block copolymers, physical blendsand alloys, two-phase graft copolymers, and blends thereof with eachother; applying an adhesion promoting compound to at least one surfaceof said window panel; forming and bonding a gasket from said selectedmaterial on said adhesion promoting compound on said at least onesurface of said window panel; providing an attachment member forsecuring said vehicle window panel assembly to a vehicle body; embeddinga first portion of said attachment member in said gasket duringformation of said gasket such that a second portion of said attachmentmember extends from said gasket for securement to the vehicle body,whereby said gasket is securely bonded to said one surface of saidwindow panel and said melt-processible polymeric material resists creepwhen said window panel is attached to a vehicle with said attachmentmember.
 27. A product made according to the method as defined in claim26.
 28. A method for manufacturing a vehicle window panel assemblycomprising the steps of:providing a window panel; selecting amelt-processible, polymeric material capable of forming cross-links;forming and adhering a gasket on at least one surface of said windowpanel from said melt-processible polymeric material; providing anattachment member adapted to secure said vehicle window panel assemblyto a vehicle body; and embedding a first portion of said attachmentmember in said gasket and cross-linking said melt-processible materialduring formation of said gasket such that a second portion of saidattachment member extends from said gasket for securement to the vehiclebody, whereby said gasket is securely bonded to said one surface of saidwindow panel and said cross-linked polymeric material of said gasketresists creep when said window panel is attached to the vehicle withsaid attachment member.